Role of Airway Derived Extracellular Vesicles (EVs) in Respiratory Viral Infections

There is a great and unmet need to develop new pharmacologic approaches to prevent and treat respiratory viral infections which are the cause of acute and chronic lung morbidity. Among these pathogens, respiratory syncytial virus (RSV) is well recognized as a major cause of bronchiolitis and pneumonia in young children and older adults, with no vaccine or specific antiviral therapy currently available. Our laboratory and the applicant of this Catalyst Award have pioneered work focused on the isolation and structural characterization of subcellular fractions known as extracellular vesicles (EVs), which are released by airway epithelial cells under different experimental conditions. EVs have a stable and “protected” structure, i.e. proteins that are carried within EVs can travel to distant sites and maintain their biological function. We have found that: i) EVs from viral-infected human airway epithelial cells contain both type I and type III interferons (IFNs), which are biologically active and inhibit viral replication in recipient cells; and ii) EVs can be isolated from upper airway secretions of patients with episodes of respiratory viral infections. The immune cargo of upper airway EVs and its antiviral activity are largely uncharacterized and therefore are central to this proposal. Based on our work and this gap in the knowledge, we hypothesize that EVs released in the upper airway mucosa (nose), following RSV infection, function as antiviral messengers by carrying critical innate mediators that can protect the lung from infection. The applicant will test this hypothesis by pursing three specific aims: Aim 1 is to characterize the immune cargo of EVs generated by upper airways, using an in vitro model of viral-infected human nose organoids (HNOs). Aim 2 is to determine the antiviral activity of upper airway EVs on recipient lung epithelial cells infected with RSV. Aim 3 is to profile the innate immune cargo of EVs isolated from the nasopharyngeal secretions (NPS) of children with episodes of RSV bronchiolitis and test their antiviral properties. The feasibility of this experimental design is supported by the applicant’s preliminary data, including evidence that EVs can be isolated and rigorously characterized by established protein markers from air-liquid-interface (ALI)-differentiated HNOs cultures, and from patient NPS samples. These studies will establish a novel and uncharted model of crosstalk between the upper airways and the lung, highly relevant to other diseases of the lung, such asthma or COPD which are often triggered by upper respiratory tract infections. The rigorous scientific training and outstanding mentorship offered to the applicant by this Catalyst Award will be instrumental in guiding future steps towards her independent research in the area of viral respiratory infections, molecular characterization of epithelial subcellular fractions and lung immunopathogenesis.